It estimates the fraction of the sky which is visible from the point, a number between 0 and 1.
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The sky view factor is 1 in a flat area and it decreases in a valley, the more narrow the valley is, the smaller it is. 
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The algorithm implemented is derived from <i>Corripio:2003</i>.
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<h3>Inputs</h3>
<ul>      
<li>the file containing the matrix of the elevations, usually the DEM or the output of pitfiller </li>
</ul>
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<h3>Output</h3>
<ul>      
<li>the file containing the sky view factor matrix (as numbers between 0 and 1)</li>
</ul>